[...]. That being said…
Are not
\relative f'
and
\fixed c'''
just "feature requests for laziness with resulting opaqueness"? ;)
[...]
We (well… modulo me LOL) don’t get this worked up about how \relative makes cut-and-paste a nightmare. Why start now? ;)
Some lilypond users get vaccinated against \relative issues and they are using it without any problem (it's not my case). So looks pretty clear you can live and get profit from \relative.
Personally I really don't like \relative: it always cause problems to me but maybe there are also aesthetic reasons for my aversion.
As I previously said (few months ago) \relative is another thing that in my opinion should be handle by the editor.
Copy and paste issues with relative is only another bad things but for me it's not the main one. For example I consider perfectly acceptable copy and paste issues with Python indention because the benefits largely outweigh the drawbacks imho.
G.